Magnet Design Guide – Learn How to Make Your Magnets
Designing your magnets can be an overwhelming task without the right information. It does not matter the type of magnet design you want – it is critical to consider possible shapes, materials, magnetic performance characteristics, and uses among others.
Once you understand these 4 principles for magnets design, the process will be seamless and straightforward.
Step 1: Know the Magnet Design or Shape
First, you must know the magnet design shape you want. In most cases, the applications will determine the magnet shape.
Of course, there are those we consider “standard” while others are custom designs. Whenever you have magnet design ideas, consider the following:
Although these are some of the most common magnet design shapes, you can also choose custom options for your project design. However, working with standard design will make the entire magnet design process easier and simple.
Magnet Design Guide – Learn How to Make Your Magnets
Step 2: Choosing Magnet Material
Whichever magnet design ideas you have, knowing the right magnetic material is paramount. Some popular magnetic materials for your personalized magnets include:
Depending on the specific requirements, the magnet design engineer will advise on the right magnetic material.
All these magnetic materials vary in magnetic strength, magnetizing force, working temperature, and magnetic flux density, among other critical variables.
Therefore, you will choose these variables depending on your personalized custom magnet design requirements. They will determine how to use the magnets.
Remember, they are available in different material grades for specialized applications.
Step 3: Understanding Magnetic Parameters
How to make a magnet requires careful understanding and analysis of various magnetic parameters. That is, you must evaluate all the intended environmental conditions and working parameters.
To design your magnets, you should consider the following key variables:
1. Finite Element Analysis (FEA)
FEA is modeling criteria that help you arrive at a suitable magnet design. Through various simulations, you can analyze the magnets:
Flux density
Torque
Magnetic forces
These magnetic design software will help you develop information on:
Flux paths
Vector magnetic potential
Flux density
Usually, working closely with magnet design engineers will help you get accurate parameters from the simulation process.
2. Understand the B-H Curve Characteristics
This magnet curve illustrates the relationship between:
Magnetic flux density; is usually denoted by B;
Magnetizing force; is denoted by H.
When it comes to the magnet design guide principle, you must evaluate the B-H curve/hysteresis loop.
With the B-H curve, it is easier to characterize various magnet materials. You will learn all the fundamental aspects during the magnets design process. It is a closed loop showing:
Magnet saturation phase
Demagnetization phase
Magnet saturation (thou in the opposite demagnetization)
Demagnetization phase
Theoretically, you can experience this under the influence of an external force. You can see this illustrated in the Cartesian plane below for the B-H curve:
3. Important Calculations in Magnet Design
There are many magnet simulation software for the design process. Of course, they all depend on certain mathematical modeling to get possible magnet designs and requirements.
In this section, we shall explore some fundamental equations that will help you design the magnets.
Calculating: Magnet Length, Pole Area, and Permeance Coefficient
4. Strive for Stability in the Permanent Magnet Design
Different shapes of magnet design have varying stability thresholds. Usually, during the magnet manufacturing process, the magnetization will align the poles in a specific direction.
Once that occurs, they are “locked” in that position. However, there is a certain phenomenon that can interfere with the normal operation of the magnet.
In the worst case possible, they may cause demagnetization.
Again, a principle magnet design guide dictates that the magnet should maintain its repeated magnetic performance. We refer to such a situation as magnet stability.
Therefore, even as you design magnets, pay attention to:
Duration you Expect Magnet to Remain in Use
Electromagnets will remain magnetic as long as they are energized (availability of electric current).
However, permanent magnets will retain their magnetic force for a long time.
But again, after manufacturing magnets and subsequent magnetizations, they tend to lose a certain percentage of their magnetic strength. However, this loss is very small and cannot affect the normal working of the magnet.
In most instances, the magnet may have unstable domains. It is within these domains that these losses occur. A phenomenon called magnetic creep.
Once the number of unstable domains reduces, your magnet will retain the net magnetic effect for a very long time.
For some magnets such as samarium cobalt, the loss can be between 0% and 3% after nearly 10 years.
Effects of Temperature on the Magnet
The surrounding temperature where you intend to use the magnet also matters very important. Usually, the effects of temperature on magnetic properties may be reversible or irreversible.
However, for the irreversible losses, some you can recover, and some you may not. Well, that sounds interesting – you will learn more about that shortly.
Magnetic Material Curie Temperature (ºC) Maximum Temperature (ºC)
Ferritic or ceramic magnets 460 300
Neodymium 310 150
Samarium cobalt 750 300
Alnico 860 540
From this information, it is quite clear – if custom magnet designs are for high-temperature applications, then choose Alnico. For low-temperature applications, go for neodymium magnets. However, you must consider other factors such as resistance to corrosion, magnetic strength, ease of machinability, etc.
Temperature is just one variable.
Again in the table above, the maximum temperature refers to a range within which you can operate the magnet. The recommended working temperature.
The Curie temperature is a point where the magnet becomes completely demagnetized.
Now, let’s compare the various temperature conditions:
Classifying Temperature Situations in Magnets Effects of Temperature on Magnets
Reversible losses
Magnet retains its original property after temperature returns to normal condition
It varies depending on the magnetic material grade
Losses are irreversible however, you can recover the properties
It is partial demagnetization
You can restore magnetic properties through re-magnetization
Even if the magnet returns to normal temperature, it will not recover the magnetic properties by itself
Irreversible and unrecoverable losses
You cannot recover the lost magnetic properties through re-magnetization
At this stage, there are significant changes in the magnet’s metallurgical structure
With these in mind, how then does this contribute to designing a stable magnet?
Demagnetization may help achieve magnet stability. That is, you will expose the magnet to high temperatures thou the process must be controlled.
It will help achieve stabilized magnetism since magnet domains with low commitment will lose their magnetism
In stabilized magnets, the flux variation will be low.
Analyze Effects of External Magnetic Fields
Again, this comes to understanding where you will use the magnet. Remember, repulsive external magnetic fields can cause demagnetization.
Therefore, you should know the magnet’s coercive force. In most cases, rare earth magnets are difficult to demagnetize by an external magnetic field.
Types of magnetic fields
Types of Magnetic Fields – Source: Science Facts
Effects of Radiation on Magnets
Magnets such as Sm2Co17 can withstand radiation better than neodymium magnets. However, some magnets get demagnetized on exposure to a significant amount of radiation.
Mechanical Impact on Magnets
Mechanical impact range from vibration, shock, or stress. Again, this requires you to understand specific applications or where you intend to use the custom magnet design.
Although modern magnets can withstand a significant amount of shock, there are inherently brittle magnets.
For instance;
Thermal shock can damage samarium cobalt and ferrite magnets
Mechanical shock can break samarium cobalt magnets due to their fragility
Step 4: Understand the Manufacturing Magnet
Magnet manufacturing is also an important factor to consider during the magnet design process.
We have a complete guide here on Different Ways to Manufacture Magnets. Remember, a manufacturing process can only be suitable for specific magnet designs.
Let’s summarize some important magnet manufacturing processes:
Magnet Manufacturing Technique Types of Magnet Designs
Sintering magnets
Rare earth magnets
Alnico magnets
Ferrite magnets or ceramic magnets
Injection molding magnets
Ceramic magnets or ferrite magnets
Rare earth magnets
Pressure bonding magnets
Rare earth magnets
Ceramic magnets or ferrite magnets
Casting magnets
Alnico magnets
Extruding magnets
Neodymium magnets
Flexible magnets
Calendering magnets manufacturing
Flexible magnets
Therefore, even as you choose your magnets design, it is important to specify the recommended manufacturing process.
The manufacturing should cover every process, from material selection to magnetization and quality testing.
Remember, when it comes to evaluating the magnet’s manufacturing process, you must consider other factors such as:
Machining operations – these may involve grinding, cutting, or drilling to achieve certain surface finishes
Coating – some magnets may require coating for additional protection. This is to protect the magnet from corrosive environments that can cause rusting. For instance, neodymium magnets are not corrosion-resistant. Therefore, they require coating.
Magnet Assembly – you may use adhesive or fasteners to assemble magnets in various applications.
Quality Testing Magnet After Design and Manufacturing
Through quality testing, you can establish if you have a good design for your magnet or not. There are many ways of verifying magnet quality. Some common magnet quality testing includes:
B-H curves
Determining total flux
Measuring the flux density
Conducting pull-up tests
Step 5: Specify Uses of Custom Magnets
There are different shapes of magnet designs available for various applications. Remember, the magnet shape, material type, and performance characteristics determine specific magnet applications.
Generally, the available magnet designs perform 4 fundamental functions:
The function of a Magnet Examples of Applications
Mechanical to mechanical energy
Magnets either attract or repel certain components. The phenomenon can either be in a linear, rotary, or reciprocating motion.
Mechanical to electrical energy
They convert kinetic energy into electrical energy like in the case of generators
Converting electrical energy to mechanical energy
Some examples are magnetostrictive materials. Another example is the electric motors
Converting mechanical energy to heat energy
The hysteresis torque equipment and eddy current devices exhibit the conversion of mechanical energy into heat
Apart from these, there are certain instances where magnets may perform special functions such as:
Magneto resistance
Magnetic resonance
Hall effect
With these four steps, you can design and manufacture magnets easily. It doesn’t matter whether you are designing lifting magnets or sensor magnets. The fundamental principles remain the same.
Conclusion
As you can see, designing magnets is a rigorous process. You must know the material type, understand the magnet working parameters, choose a suitable magnet manufacturing process, and establish proper quality testing.